Composition based on cross-linkable, water-dissipatable acrylic polymers, process and use

ABSTRACT

A process for preparing a patterned, cross-linked, acrylic-polymer, film coating on a substrate; the process comprising the steps of: a) applying to the substrate by an ink-jet printing process a mixture comprising: i) one or more cross-linkable, thermally ink-jettable, water-dissipatable, precursor(s) for one or more cross-linked acrylic-polymer(s); ii) one or more cross-linker(s) capable of cross-linking the precursor(s) for the acrylic-polymer(s); and iii) one or more colorant(s); and b) thereafter curing the mixture in situ to form the patterned, cross-linked, acrylic-polymer, film coating on the substrate. Preferably the substrate is a color filter suitable for use in an LCD display and the mixture is applied in a single pass. The precursor may itself comprise polymers, e.g. acrylic polymers. Ink for use in this process and substrates printed by this process are also described.

This application is the National Phase of International ApplicationPCT/GB99/02989 filed Sep. 8, 1999 which designated the U.S. and thatInternational Application was published under PCT Article 21(2) inEnglish.

This invention relates to inks comprising acrylic polymers; to their usein ink jet printing to prepare patterned substrates (e.g. colourfilters); and patterned substrates prepared by this method.

Ink jet printing (IJP) methods involve a non-impact printing techniquefor printing an image onto a substrate using ink droplets ejectedthrough a fine nozzle onto a substrate without bringing the nozzle intocontact with the substrate.

The ability to produce a patterned polymeric coating on a substrate,where the coating has high resistance (fastness) to solvents, water andheat is important in many areas of for instance the electronics andprinting industries. IJP is a convenient method of producing suchpatterns in a precise and rapid manner. In this process, inks containingprecursors for cross-linked acrylic polymer(s) are applied to thesubstrate to produce a continuous film, and the substrate issubsequently treated in order to produce a cross-linking reaction withinthe film to give a coating with the requisite fastness properties. Theuse of IJP, particularly thermal IJP, does however impose significantdemands on the precursors used to produce such patterns, as they must bechosen such that they are able to produce inks of low viscosity and highstability, and yet are sufficiently reactive to produce the highfastness properties needed once they are applied to the substrate.

There are many demanding performance requirements for colorants and inksused in IJP. For example, they desirably provide sharp images havinggood water-fastness, light-fastness and optical density. The inks areoften required to dry quickly when applied to a substrate, but theyshould not form a crust over the tip of an ink jet nozzle because thiswill stop the printer from working. The inks should also be stable tostorage over time without decomposing or forming a precipitate whichcould block the fine nozzle. The most popular ink jet printers are thethermal and piezoelectric ink jet printers. There is a need for inkswhich are suitable for both thermal and piezo ink jet printers, havehigh colour strength and produce images having a high light-fastness andwater-fastness when printed on a substrate.

Colour filters, alternatively known as optical filters, are a componentof coloured liquid crystal displays (LCDs) used as flat screen displaysas, for example, in small television receivers or portable computers.Typically, a white back-light is shone through a liquid crystal layerand then a colour filter to produce an image of the desired colour bythe transmitted light. The LCD layer comprises an addressable array ofpixels. The light at any pixel can be switched on and off by applying avoltage to the liquid crystal film which changes the orientation of thepolarising liquid crystals to block the back-light. The pixels are inregister with a trichromatic array of colour filter elements to producea full colour screen capable of displaying images. Some LCD displays areconstructed to be viewed by reflected light, but still require a colourfilter to produce a full colour image. Colour filters are equally usefulfor other display technologies such as plasma display panels, cathoderay tubes and electroluminescent displays and as a component of solidstate imaging devices. It is advantageous that the coloured elements ofa colour filter are formed by a printing process such as IJP. Comparedto other methods (e.g. etching or photolithography) the wastage ofcolorant is much less and the manufacturing steps are reduced, leadingto a simpler and cheaper process.

For the IJP of colour filters it is important to maximise the solidscontent of the ink formulation to enhance film quality and minimise thenumber of processing steps. This must be achieved whilst maintaining lowink viscosity. It is particularly preferable to be able to achievesufficiently high solids loadings in the ink to allow the deposition ofenough material on to the substrate to produce the desired properties ina single pass of the ink-jet head. It is also important that the colourfilter is resistant to solvents, water, heat and light. Such resistancecan be achieved by cross-linking polymeric components using a thermalcross-linking reaction. It is vital that cross-linking reactionsemployed do not take place in the print head if a thermal IJP method isto be used.

Certain photosensitive acrylic resins have previously been used toproduce colour filters by photolithography, which, as mentioned above,is a wasteful and complicated process. Much of the colorant that isapplied to the substrate is removed in later process steps. Thesephotosensitive acrylic resins are not applied by IJP, and are unsuitablefor such a process, particularly in the demanding conditions experiencedin a thermal ink-jet print head.

WO 95-034024 (Zeneca) (=EP 0764290) discloses a method for producing acolour filter by IJP a precursor for a polymer and a resin reactive dyeso that the dye is covalently attached to the cross-linked polymermatrix on the substrate surface. The polymeric inks disclosed in thisreference are not especially optimised for being fired in a thermalink-jet print head, whereas the acrylic polymers used in the presentinvention are optimised to be thermally ink-jettable. Thus for examplecertain inks disclosed in WO 95-034024 may comprise too muchmelamine-formaldehyde resin cross-linker to be fired from a thermal IJprint head (see Comparative Example A, herein). The present inventiondoes not require use of a resin-reactive colorant, where the colorant ischemically bound to the cross-linked polymer. Thus the present inventionmay use colorants incompatible with those described in WO 95-034024which thus teaches away from the present invention. The ability to usedyes which are not covalently bound to the polymer greatly increases theflexibility in the choice of colorant used.

JP-A-08-311383 (Canon) describes the use of an alkali solublestyrene-acrylic acid co-polymer as a pigment dispersant for a thermalink-jet ink. Although this ink uses ethanolamine as a base, this wouldnot be a particularly effective cross-linker. This document does notsuggest to cross-link the resin or to try to form a continuous film,both of which are important when making a colour filter.

JP-A-09-157563 (Kao Corp.) describes an ink which has good operabilityin a thermal ink-jet head and contains a carboxylic acid containingpolymer such as poly(ethylene-co-acrylic acid). It is believed that thepolymer is present to improve the water resistance of the dye. As withthe previous Canon reference, this document does not teach to cross-linkthe acrylic polymer or form a continuous film.

EP-A-0703471 (Canon) describes a method for producing colour filters byIJP an acrylic polymer as an ink-receiving layer. This requires applyingthe polymer and colorant in two separate stages, whereas in the presentinvention only one processing step is required to apply both colorantand polymer.

JP-A-09-090115 (Toray Ind.) discloses an ink containing a pigment,styrene-acrylic acid polymer and melamine-formaldehyde resin to form acolour filter using an IJP process. The applicant has found thatmelamine-formaldehyde resins give poor operability in a thermal ink-jethead. The inks described in the present invention also allow the use ofdyes as colorants to give filters with particularly good spectralproperties.

JP-A-09-132740 (Asahi Glass) describes the use of a resin and pigmentink for making colour filters by ink-jet, but the inks contain mixturesof colloidal silica and water dispersible resins which will not fireefficiently through a thermal print head at the high loadings requiredto produce a durable colour filter in a single pass.

JP-A-09-165541 (Kao Corp.) is similar to the previous Kao patent, butuses polymers which are cross-linked by UV and solubilised with styrenesulphonic acid comonomer. These inks are not used to form continuousfilms and are not thermally cured. Thermal curing is advantageouscompared to the alternatives such as UV-curing, as thermal curing can bea non-radical process and generally less harmful to the dyes.

JP-A-08-333537 (Canon) describes a ‘thermoreversible thickening polymer’which is used as a wet fastness additive. This polymer is stated tocross-link on drying to give a water resistant film. From the examples,this appears to involve nucleophile/electrophile chemistry, with a ring—NH group as the nucleophile and an epoxide as the electrophile. Theexample given has a M_(w) of 200,000, which is much higher than thepreferred M_(w) values of polymeric precursors used in the presentinvention. The polymer is used at only 3% total resin loading so itwould not form an effective colour filter. It is unlikely that such apolymeric system would be thermally ink-jettable at the high solidsloadings needed in inks to form colour filters in a single pass process.

EP 0591916 (MAN Roland Druckmasch) describes a composition used formaking offset printing plates, involving ink-jetting a cross-linkablepolymer system formed by reacting a polyol with a poly carboxylicanhydride (e.g. poly(styrene-co-maleic anhydride) and PVA. All theexamples use no more than about 3% total resin loading in the inks,which is incompatible with a single pass process for colour filterswhere higher resin loadings are generally required (often above 10%).The MAN compositions do not contain a separate colorant. All thecross-linkers used in MAN are polymeric which the applicant has foundare not preferred in the process of the present invention as they do notreadily thermally ink-jet.

The prior art polymeric inks are not cross-linked to form colourfilters; are not reliably ink-jettable, especially not in a thermalink-jet printer; and/or are incapable producing a durable coating of across-linked acrylic-polymer film, especially in a single pass IJPprocess. There is no disclosure in the prior art of an, optionallypolymeric, ink of good operability which may be reliably andeconomically applied, optionally in a single pass, to a patternedsubstrate by an ink-jet printing process, optionally thermal IJP, toproduce after curing, optionally thermally, a coating of a resistant,patterned, coloured, cross-linked, acrylic-polymer film, optionally acolour filter.

It is an object of the present invention to provide improved processesfor forming film coatings, that overcome some or all of thedisadvantages of the prior art as discussed above.

Surprisingly the applicant has found that inks containing one or moreprecursor(s) for cross-linked acrylic polymer(s), cross-linking agent(s)and colorant(s) are particularly suitable for making colour filters by aprinting process, optionally IJP, particularly thermal IJP. Althoughthese inks offer particular advantages when used in a thermal ink-jethead, they are also suitable for use in piezoelectric IJP and offerimproved reliability over the prior art for this technology.

According to a first aspect of the present invention, there is provideda process for preparing a patterned, cross-linked, acrylic-polymer, filmcoating on a substrate; the processing comprising the steps of:

a) applying to the substrate by an ink-jet printing process, optionallyin a single pass, a mixture comprising:

i) one or more cross-linkable, thermally ink-jettable,water-dissipatable precursor(s) for one or more cross-linkedacrylic-polymer(s);

ii) one or more cross-linker(s) capable of cross-linking theprecursor(s) for the acrylic-polymer(s); and

iii) one or more colorant(s); and

b) thereafter curing the mixture in situ, to form the patterned,cross-linked, acrylic-polymer, film coating on the substrate.

Preferably the ink-jet printing process is thermal IJP.

Preferably the precursor(s) for the cross-linked acrylic-polymer(s) ispresent in the mixture in a total amount greater than about 4%.

The mixture comprises a total solids content which is both sufficientlyhigh enough to form, after curing, the film coating after the singlepass IJP process, yet is sufficiently low enough so the mixture is stillreadily printable using IJP (preferably thermal IJP). Conveniently, thetotal solids content of the mixture is from about 4% to about 50% byweight. Optionally the solids content consists substantially of the(optionally polymeric) precursor(s).

Preferably the precursor has a weight average molecular weight (M_(w))less than 200,000.

Preferably the cross-linker has a weight average molecular weight(M_(w)) less than 10,000, more preferably are non-polymeric.

Preferably the cross-linker is other than ethanolamine, more preferablyis other than ethanolamine, epoxy and/or melamine-formaldehyde resin.

Preferably the mixture is capable of being thermally cured after IJP.

Preferably the film coating is substantially continuous.

Preferably the mixture to be printed has a good operability,effectiveness and/or reliability in an IJ (preferably thermal IJ) printhead.

Preferably the process uses most (more preferably substantially all) ofthe mixture that is applied to form the final film coating, i.e. theprocess is not excessively wasteful of material.

Preferably the mixture comprises less than about 4% by weight, morepreferably is substantially free of, melamine-formaldehyde resin.

The film coating may be either a colour filter comprising a coloured,cross-linked, acrylic-polymer, film coating on a transparent substrate;or a transparent coloured; cross-linked acrylic-polymer, film coating ona substrate.

In the above process inks are applied, preferably in a single pass, to asubstrate by an ink-jet printing process and cured, preferablythermally, to give a colour filter matrix with high transparency andvery good solvent, water, heat and light resistance. Optionally a colourfilter comprises red, green and blue filter elements. Each of thecoloured inks used to form each colour component of the resultant film(e.g. a colour trichromat and black) may be applied to the substrate ina single pass for each colour. Optionally all of the inks used to formthe final coloured film may be applied simultaneously to the substrateby a multi headed IJ printer (optionally in different patterns) so thata durable, resistant full-colour film can be formed on the substrate ina single pass.

Unlike the prior art, the inks used in the above process have goodoperability in an ink-jet head (especially a thermal ink-jet head) evenat relatively high solids loadings. Although polymers have beendisclosed in the prior art for use in thermal ink-jet inks asdispersants and wet-fastness improving additives amongst others, theprior art does not disclose the use of precursors for cross-linkedacrylic polymers in thermal IJ inks in conjunction with a cross-linkerand at high solids loadings. The inks used in the present invention givehighly resistant film coatings. The precursor(s) may themselves bepolymeric, comprising one or more polymer(s), preferably one or moreacrylic polymer(s).

The above process could equally be applied to any application where across-linked film needs to be applied to a substrate in a precisepattern and is not limited to the production of coloured films, as thecolorant could be omitted. This could potentially be seen as analternative technology to photolithography, for production of printedcircuit boards, offset printing plates and other similar processes.Other possible uses for a process for applying films of the presentinvention which are coloured includes processes for coating vehicles(e.g. cars).

The thermally ink-jettable, water-dissipatable precursor(s) for theacrylic-polymer(s) have preferably been obtained from the polymerisationof one or more olefinically unsaturated monomer(s) having waterdispersing groups, optionally in the presence of one or moreolefinically unsaturated monomer(s) which are free from water dispersinggroup(s). Preferably the water-dissipatable precursor(s) arehydrophilic.

The precursor(s) may comprise one or more olefinically unsaturated,water-dissipatable monomer(s) (e.g. acrylic acid) and/or one or morepolymer(s) derivable from one or more olefinically unsaturated,water-dissipatable monomer(s), such monomer(s) and/or polymer(s)preferably being present in amount from about 20% to about 100% byweight of the precursor(s).

Preferably the number average molecular weight (M_(n)) of thoseprecursor(s) (and/or components thereof) which are polymeric is lessthan about 20,000, more preferably from about 200 to about 20,000; mostpreferably from about 200 to about 10,000; and especially from about 350to about 2,000. The M_(n) of such precursor(s) may be measured by gelpermeation chromatography (“GPC”).

The GPC method used for determining M_(n) preferably comprises applyinga polymer to a chromatography column packed with cross-linkedpolystyrene/divinyl benzene, eluting the column with tetrahydrofuran ata temperature of 40° C. and assessing the M_(n) of the polymer comparedto a number of a polystyrene standards of a known M_(n). Suitablecross-linked polystyrene/divinyl benzene chromatography columns arecommercially available from Polymer Laboratories.

If the GPC method for determining M_(n) does not work for any reason,for example the polymer has an unexpected interaction with the GPCcolumn to give an unrealistic result, the M_(n) may be determined usingalternative methods, for example by vapour phase osmometry.

The precursor(s) preferably has an acid value of from 0 to 1000 mgKOH/g,more preferably 100 to 850 mgKOH/g.

Optimisation of both molecular weight and acid content are important toachieve operability of the precursor(s) in a thermal IJ head.

It is also optional that the precursor(s) comprises a mixture ofdifferent polymers as this may help reduce the presence of defects suchas pinholes in the polymer film produced by the process of the presentinvention.

The precursor for the cross-linked acrylic-polymer used in the presentinvention comprises any thermally ink-jettable and water-dissipatablemoiety which is capable of being polymerised to form an acrylic polymer.The precursor(s) may itself comprise monomeric, oligomeric and/orpolymeric components and/or mixtures thereof. The precursor may be asingle component or a mixture. Preferably the precursor compriseshydrocarbyl and/or heterocarbyl chains (preferably C₂-C₁₅₀alkyl) whichare substituted by one or more acid functional group(s) preferablyselected from carboxy, carboxy substituted alkyl and carboxy substitutedaryl. Such groups can be chain pendant and/or terminal. The precursor(s)for the cross-linked acrylic polymer(s) may itself optionally compriseone or more acrylic polymer(s), preferably acrylic polymer(s) of lowmolecular weight (e.g. M_(n) less than about 20,000).

Preferably the precursor is selected from one or more of: homopolymersof (meth)acrylic acid, vinyl acetic acid, crotonic acid, itaconic acid,maleic acid, citraconic acid, fumaric acid or 2,4-pentadienoic acid;co-polymers of these monomers with each other or with other monomers(for example one or more selected from alkyl [meth]acrylates andstyrene); and monomeric poly carboxylic acids (for example butane1,2,3,4-tetracarboxylic acid).

The cross-linker preferably comprises a poly-nucleophile functionalisedcompound (e.g. a di- or poly-alcohol), amine or thiol. More preferablythe cross-linker is selected from one or more diol(s); polyol(s)comprising three or more hydroxy groups (for example that availablecommercially from EMS Chemie under the trade name Primid XL552);trimethylolpropane; and triethanolamine. A less preferred cross-linkercomprises poly(vinyl alcohol) [PVA] which gives a resultant polymer withgood fastness properties, but tends to cross-link too extensively,making it difficult to find dyes which are compatible with the resultantpolymer matrix. Polyamines may also be used as cross-linkers but theyalso are less preferred as they tend to give films with poorer fastnessproperties.

For the purposes of the present invention the term “colorant” as usedherein denotes perceptible and/or emissive materials. The term“perceptible material” as used herein includes all dyes and/or pigmentsand denotes materials which absorb radiation substantially in that partof the electromagnetic (EM) spectrum which encompass the infra red (IR);visible and/or ultraviolet (UV) regions, preferably in a region wherethe radiation wavelength [λ] is from about 200 nm to about 800 nm, morepreferably in the visible region which is detectable by the normal,unaided human eye. The term “emissive material” as used herein denotes amaterial which is capable of emitting radiation, preferably EMradiation, more preferably radiation in the IR, visible and/or UVregions of the EM spectrum. Examples of emissive materials comprisefluorescent, phosphorescent and/or radioactive materials.

The dispersing groups in the precursor for the acrylic-polymer providethe facility of self-dispersibility and solubility to the precursor inink media, especially in water. The dispersing groups may be ionic,non-ionic or a mixture of ionic and non-ionic dispersing groups.Preferred ionic dispersing groups include cationic quaternary ammoniumgroups and acid groups, for example phosphonic acid groups, sulphonicacid groups and carboxylic acid groups.

The dispersing groups may be incorporated into the precursor in the formof monomers or oligomers bearing the appropriate dispersing groups. Onemay also react a precursor which is not water-dissipatable, withmonomers or oligomers which make the precursor water-dissipatable.

The acid groups may be subsequently fully or partially neutralised witha base containing a cationic charge to give a salt. If the aciddispersing groups are used in combination with a non-ionic dispersinggroup, neutralisation may not be required. The conversion of any freeacid groups into the corresponding salt may be effected during thepreparation of the precursor and/or during the preparation of an inkfrom the precursor.

Preferably the base used to neutralise any acid dispersing groups isammonia, an amine or an inorganic base. Suitable amines are tertiaryamines, for example triethylamine or triethanolamine. Suitable inorganicbases include alkaline hydroxides and carbonates, for example lithiumhydroxide, sodium hydroxide, or potassium hydroxide. A quaternaryammonium hydroxide, for example N⁺(CH₃)₄OH⁻, can also be used. Generallya base is used which gives the required counter ion desired for an inkwhich is prepared from an acrylic polymer. For example, suitable counterions include Li⁺, Na⁺, K⁺, NH₄ ⁺ and substituted ammonium salts.

Non-ionic dispersing groups may be in-chain, pendant or terminal groups.Preferably non-ionic dispersing groups are pendant polyoxyalkylenegroups, more preferably polyoxyethylene groups. The non-ionic groups maybe introduced into the precursor (which may itself be an acrylicpolymer) in the form of a compound bearing non-ionic dispersing groupsand at least one (although preferably only one) co-polymerisableolefinically unsaturated group.

The nature and level of dispersing groups in the precursor influenceswhether a solution, dispersion, emulsion or suspension is formed ondissipation of the precursor.

The dispersing group content of the precursor for the acrylic-polymermay vary within wide limits but is preferably sufficient to make theprecursor form stable IJP inks in water and aqueous media. The precursoris preferably soluble in water, although minor amount of the precursormay be insoluble in water and exist as dissipated particles when mixedwith aqueous media or water.

Preferably the proportion of insoluble, water-dissipatable precursor forthe cross-linked acrylic polymer is less than 50%, preferably less than40% and most preferably less than 30% by weight relative to the totalweight of the precursor. The size of insoluble precursor particulateswhen dissipated in an ink is preferably less than 100 nm, and morepreferably less than 60 nm.

Preferably the precursor for the cross-linked acrylic-polymer filmcoating is itself polymeric, more preferably it comprises one or moreacrylic polymer(s).

A precursor which is polymeric may be prepared by polymerisation of:

(a) olefinically unsaturated monomers providing dispersing groups in thepresence of

(b) olefinically unsaturated monomers which are free from dispersinggroups.

It is preferred that the amount of (b) is from 0 to 95%, more preferablyfrom 2 to 90% by weight relative to the weight of (a)+(b).

A precursor which is polymeric may be prepared in a conventional mannerby polymerising the olefinically unsaturated monomers providingdispersing groups either alone or in the presence of olefinicallyunsaturated monomers which are free from dispersing groups. Temperaturesof between 20° C. and 180° C. are preferred. The polymerisation may becontinued until reaction between the monomers is complete.

In one embodiment used in the present invention a precursor which ispolymeric may be prepared by polymerising an acrylic oligomer havingwater dispersing groups and one olefinically unsaturated terminal groupin the presence of one or more olefinically unsaturated monomers whichare free from water dispersing groups and/or olefinically unsaturatedmonomers having water dispersing groups. Alternatively an acrylicoligomer which is free from water dispersing groups may be polymerisedin the presence of one or more olefinically unsaturated monomers havingwater dispersing groups.

Preferred polymerisation methods include solution polymerisation,emulsion polymerisation, suspension polymerisation andsolution/dispersion polymerisation and such general methods are wellknown in the art.

If desired, an initiator may be used to assist formation of thoseprecursor(s) which themselves are polymer [e.g. comprise acrylicpolymer(s)]. Suitable initiators are free-radical generators. Examplesof catalysts include azobis compounds, peroxides, hydroperoxides, redoxcatalysts, etc., for example, potassium persulphate, ammoniumpersulphate, tert-butyl peroctoate, benzoyl peroxide, isopropylpercarbonate, 2,4-dichlorobenzoyl peroxide, methyl ethyl ketoneperoxide, cumene hydroperoxide, dicumyl peroxide,azobisisobutyronitrile, azobis(2-amidino-propane)hydrochloride and thelike.

Typically 0.05 to 5% by weight of initiator is used relative to thetotal weight of the monomers. Preferably the polymerisation is performedin the presence of an emulsifying agent.

The M_(n) of a precursor which is polymeric may be controlled by theaddition of chain transfer agents and/or through the adjustment of theratio of the concentration of monomers relative to the concentration ofinitiator during the course of the polymerisation. Typical chaintransfer agents are thiols, halocarbons and cobalt macrocycles.

Preferred olefinically unsaturated monomers providing ionic dispersinggroups include acrylic acid, methacrylic acid, itaconic acid, maleicacid, fumaric acid, pentadienoic acid, monoalkyl itaconates (forexample, monomethyl maleate, monoethyl maleate, monobutyl maleate andmonooctyl maleate), citraconic acid, styrene sulphonic acid, vinylbenzylsulphonic acid, vinyl sulphonic acid, acryloyloxyalkyl sulphonic acids(for example, acryloyloxymethyl sulphonic acid, acryloyloxyethylsulphonic acid, acryloyloxypropyl sulphonic acid and acryloyloxybutylsulphonic acid), methacryloyloxyalkyl sulphonic acids (for examplemethacryloyloxymethyl sulphonic acid, methacryloyloxyethyl sulphonicacid, methacryloyloxypropyl sulphonic acid and methacryloyloxybutylsulphonic acid), 2-acrylamido-2-alkylalkane sulphonic acids (forexample, 2-acrylamido-2-methylethane sulphonic acid,2-acrylamido-2-methylpropane sulphonic acid and2-acrylamido-2-methylbutane sulphonic acid),2-methacrylamido-2-alkylalkane sulphonic acids (for example,2-methacrylamido-2-methylethane sulphonic acid,2-methacrylamido-2-methylpropane sulphonic acid and2-methacrylamido-2-methylbutane sulphonic acid), mono-(acryloyloxyalkyl)phosphates [for example, mono(acryloyloxyethyl) phosphate andmono(3-acryloyloxypropyl) phosphate] and mono(methacryloyloxyalkyl)phosphates [for example, mono(methacryloyloxyethyl) phosphate andmono(3-methacryloyloxypropyl) phosphate].

Preferred olefinically unsaturated monomers providing non-ionicdispersing groups include alkoxy polyethylene glycol (meth)acrylates,preferably having a number average molecular weight (M_(n)) of from 350to 2000. Examples of such monomers which are commercially availableinclude ω-methoxypolyethylene glycol acrylate (mean polymerisationdegree of polyethylene glycol is about 9) and diethylene glycol vinylether.

Preferred olefinically unsaturated monomers which are free fromdispersing groups include alkyl(meth)acrylates, optionally substitutedstyrenes, methacrylamides, allyl compounds, vinyl ethers, vinyl ketones,vinyl halides, olefins and unsaturated nitriles.

Preferred alkyl(meth)acrylates contain less than twenty carbon atoms.Examples include methyl acrylate, ethyl acrylate, n-propyl acrylate,isopropyl acrylate, n-butyl acrylate, isobutyl, sec-butyl acrylate, amylacrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate,tert-octyl acrylate, 2-phenoxyethyl acrylate, 2-chloroethyl acrylate,2-bromoethyl acrylate, 4-chlorobutyl acrylate, cyanoethyl acrylate,2-acetoxyethyl acrylate, dimethylaminoethyl acrylate, benzyl acrylate,methoxybenzyl acrylate, 2-chlorocyclohexyl acrylate, acrylate,cyclohexyl acrylate, furfuryl acrylate, tetrahydrofurfuryl acrylate,phenyl acrylate, 5-hydroxypentyl acrylate, 2,2-dimethyl-3-hydroxypropylacrylate, 2-methoxyethyl acrylate, 3-methoxybutyl acrylate,2-ethoxyethyl acrylate, 2-iso-propoxyethyl acrylate, 2-butyoxyethylacrylate, 2-(2-methoxyethoxy)ethyl acrylate, 2-(2-butoxyethoxy)ethylacrylate, 1-bromo-2-methoxyethyl acrylate, 1,1-dichloro-2-ethoxyethylacrylate, methyl methacrylate, ethyl methacrylate, n-propylmethacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutylmethacrylate, sec-butyl methacrylate, amyl methacrylate, hexylmethacrylate, cyclohexyl methacrylate benzyl methacrylate, furfurylmethacrylate, 2-hydroxyethyl methacrylate, chlorobenzyl methacrylate,octyl methacrylate, N-ethyl-N-phenylaminoethyl methacrylate,2-(3-phenylpropyloxy)ethyl methacrylate, dimethylaminophenoxyethylmethacrylate.

Preferred optionally substituted styrenes include styrene, methylstyrene, dimethyl styrene, trimethyl styrene, ethyl styrene, diethylstyrene, isopropyl styrene, butyl styrene, hexyl styrene, cyclohexylstyrene, decyl styrene, chloromethyl styrene, trifluoromethyl styrene,ethoxymethyl styrene, acetoxymethyl styrene, methoxy styrene,4-methoxy-3-methyl styrene, dimethoxy styrene, chloro styrene, dichlorostyrene, trichloro styrene, tetrachloro styrene, pentachloro styrene,bromo styrene, dibromo styrene, iodo styrene, trifluoro styrene and2-bromo-4-tri-fluoromethyl styrene.

Preferred (meth)acrylamides contain less than 12 carbon atoms. Examplesinclude methyl methacrylamide, tert-butyl methacrylamide, tert-octylmethacrylamide, benzyl methacrylamide, cyclohexyl methacrylamide, phenylmethacrylamide, dimethyl methacrylamide, dipropyl methacrylamide,hydroxyethyl-N-methylmethacrylamide, N-methylphenyl methacrylamide,N-ethyl-N-phenyl methacrylamide methacrylhydrazine and methylolmethacrylamide.

Preferred allyl compounds include allyl acetate, allyl caproate, allylcaprylate, allyl laurate, allyl palmitate, allyl stearate, allylbenzoate, allyl acetoacetate, allyl lactate, allyl oxyethanol, allylbutyl ether and allyl phenyl ether.

Preferred vinyl ethers contain less than 20 carbon atoms. Examplesinclude methyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, octylvinyl ether, decyl vinyl ether, ethylhexyl vinyl ether, methoxyethylvinyl ether, ethoxyethyl vinyl ether, chloroethyl vinyl ether,1-methyl-2,2-dimethylpropyl vinyl ether, 2-ethylbutyl vinyl ether,hydroxyethyl vinyl ether and dimethylaminoethyl vinyl ether.

Preferred vinyl ketones contain less than 12 carbon atoms. Examplesinclude methyl vinyl ketone, phenyl vinyl ketone and methoxyethyl vinylketone.

Preferred vinyl halides include vinyl chloride, vinylidene chloride andchlorotrifluoro ethylene.

Preferred olefins includes unsaturated hydrocarbons having less than 20carbon atoms. Examples include dicyclopentadiene, ethylene, propylene,1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene,1-decene, 5-methyl-1-nonene, 5,5-dimethyl-1-octene, 4-methyl-1-hexene,4,4-dimethyl-1-pentene, 5-methyl-1-hexene, 4-methyl-1-heptene,5-methyl-1-heptene, 4,4-dimethyl-1-hexene, 5,5,6-trimethyl-1-heptene,1-dodecene and 1-octadecene.

Preferred unsaturated nitriles include acrylonitrile andmethacrylonitrile.

The preferred olefinically unsaturated monomers which are free fromdispersing groups are the alkyl (meth)acrylates containing less than 20carbon atoms, especially those specifically listed above.

The precursor of the present invention may be purified if desired in theusual way for colorants used in ink jet printing inks. For example amixture of the precursor and water may be purified by ion-exchange,filtration, reverse osmosis, dialysis, freeze-drying, ultra-filtrationor a combination thereof. In this way one may remove co-solvents usedfor the polymerisation, low molecular weight salts, impurities and freemonomers.

In one optional aspect of the invention the colorant can be “resinreactive” that is be capable of forming a covalent bond with anygroup(s) of, or attached to, the precursor(s) or cross-linker(s). Acolorant is resin reactive if it can bond covalently to the precursorand/or cross-linker either via one or more heterocyclic NH group(s) in aheterocyclic part of the colorant or via substituent groups attached tothe colorant. The term “bonding covalently” will be understood toinclude both direct covalent bonds between the colorant and theprecursor and/or cross-linker, as well as indirect attachments such asvia optionally substituted alkyl or aryl groups. Thus preferred resinreactive colorant(s) comprise any heterocyclic NH group(s) or anysubstituent(s) capable of forming a covalent bond with substituentsselected from —OH; —NH₂; —NHalkyl; —SH; —COOH, —COOalkyl; epoxy;—NHCOalkenyl; and —COalkenyl. The term heterocyclic NH group means an NHgroup in which the nitrogen atom forms part of a heterocyclic ring andwhich is capable of forming a covalent bond with an acrylic polymer. Inthe patterned substrate, a resin reactive colorant would be chemicallybound within the cross-linked polymer matrix.

In another aspect of the invention the colorant is resin inactive, thatis incapable of forming a covalent bond with the precursor and/orcross-linker. In the patterned substrate, a resin inactive colorantwould be physically trapped within the spaces inside the cross-linkedpolymer matrix. Thus resin inactive colorants comprise all colorantswhich are other than the resin reactive colorants mentioned above, butotherwise effective for use in the process of the present invention.Preferred resin inactive colorants, would comprise those colorants whichalso do not exhibit the properties of the preferred resin reactivecolorants also described above.

The colorants are preferably compatible with the resultant cross-linkedacrylic-polymer coatings, i.e. the resultant cured films have hightransparency. Preferably the colorant is insoluble in organic solventsand soluble in water, for example the colorant may contain sulpho orcarboxy groups.

The colorant may be a single coloured component or a mixture of colouredcomponents, for example it may be a mixture of different colorants. Byusing a mixture of different colorants, one may achieve greaterflexibility in colour of the ink. Preferably to make a colour filtercolorants are used individually or in mixtures to give yellow, magentaand cyan inks, more preferably to give red, blue and green inks.

Preferably for use in the process of the present invention thecolorant(s) comprise dye(s). Dyes have advantages over pigments in thatless dye is usually required than would be the case for a pigment,expensive milling is avoided, inks comprising dyes are less likely toform a precipitate on standing, a far greater variety of shades areavailable and the resultant films have good chroma and transparency.

In a preferred embodiment the colorant comprises dye(s) which are watersoluble or soluble in organic solvents and insoluble in water (e.g.present as a dispersion, i.e. a disperse dye). More preferably the dyeis water soluble to improve operability.

If a water insoluble dye is used, the dye is preferably present as afine dispersion, prepared by for example milling the dye in water in ahorizontal shaker in the presence of glass or metal beads and adispersant. Suitable dispersants may comprise an anionic type (forexample lignosulphonates and other sulphonated aromatic species) or anon-ionic type (for example alkylene oxide adducts).

Useful classes of colorants include azos (including metallised azos),anthraquinones, phthalocyanines, pyrrolines, thiophenedioxides,triphenodioxazines, methines, benzofuranones, benzodifuranones,coumarins, indoanilines, benzenoids, xanthenes, triphenylmethanes,nitros, nitrosonaphthols, phenzines, solvent soluble sulphur dyes,quinophthalones, pyridones, aminopyrazoles, pyrollidines, pyrroles,styrylics, maleimides, triphenazonaphthylamines, styryls, dithenes,azomethines, cyanines, pyrrolines and azoics.

The Colour Index International lists suitable water soluble dyes such asacid dyes, direct dyes, basic dyes and reactive dyes and furtherexamples of acid dyes are given in the Color Index, 3rd Edition, Volume1, pages 1003 to 1561, further examples of direct dyes are given inVolume 2, pages 2005 to 2478, further examples of basic dyes are givenin Volume 1, pages 1611 to 1688 and further examples of reactive dyesare given in Volume 3 pages 3391 to 3560. These dyes are included hereinby reference. Preferred dyes are selected from the monoazo, disazo,metallised azo, phthalocyanine, xanthene, triphenylmethane,anthraquinone, triphendioxazine, quinophthalone, maleimide,nitrosonaphthol dye classes. Examples of preferred dyes include: AcidBlue 9, Acid Red 1, Acid Red 37, Acid Red 52, Acid Red 289, Acid Yellow3, Acid Yellow 23, Direct Blue 86, Direct Blue 87, Direct Blue 199,Direct Yellow 86, Reactive Blue 14 Reactive Blue 15 and Reactive Red 4.

Subject to the provisos herein, generally preferred colorants are thosewhich have substituent groups which aid the solubility of the dye(s) inliquid media used in the process or which aid the solubility of thedye(s) in the final cross-linked polymer matrix.

The cross-linked polymeric film coating may be formed on a substrate towhich the coating will bond, adhere, absorb or fuse. Suitabletransparent substrates include glass; plastics films and plates such asthose of polyvinylalcohol, polyester, polyvinylchloride,polyvinylfluoride, polycarbonate, polystyrene, polyamide or polyimide.The substrate may be flexible or may be a flat panel (e.g. as used inmany LCD displays). A preferred substrate is glass.

The substrates may be pre-treated to improve bonding, adhesion,absorption, fusion or spreading of the cross-linked polymeric coating onthe substrate. Suitable pre-treatments include plasma etching in whichthe substrate is placed in an oxygen atmosphere and subjected to anelectrical discharge or application of an adhesion promoter such as asilane.

In the present process the cross-linking of the precursor(s) for thecross-linked acrylic-polymer(s) may be initiated thermally, chemicallyor photochemically, although thermal initiation is preferred.

The mixture of precursor(s) for the cross-linked acrylic polymer(s),cross-linker(s) and colorant(s) can be used to give patterned,transparent films and coatings on substrates in general, includingsubstrates which are not transparent. Accordingly the present inventionincludes a process for preparing polymeric film coatings for substratesin general not just colour filters.

Chemical initiation may be achieved by addition of agents such as acidsand tertiary amines.

Photochemical initiation may be achieved by addition of initiators forexample azides, ketones such as acetophenone or benzophenone, ketalssuch as benzyldimethyl ketal, peroxides such as benzoyl peroxide or arylsulphonium salts such as diphenyl-(4-phenylthio)-phenyl sulphoniumtetrafluorophosphate, followed by irradiation with UV or visible light.

Thermally initiated cross-linking is preferably carried out at atemperature of between 100° C. and 250° C., more preferably between 120°C. and 240° C. and especially between 150° C. and 230° C. The films arecured for between 1 and 60 minutes, preferably for between 5 and 45minutes.

Thermally initiated cross-linking is preferred since it is simpler thanchemical or photochemical initiation as there is no need to addinitiators and the like to the mixture.

According to a further feature of the present invention there isprovided a composition comprising a mixture comprising one or morecross-linkable, thermally ink-jettable, water-dissipatable precursor(s)for cross-linked acrylic polymer(s); one or more cross-linker(s) capableof cross-linking the precursor(s); and one or more colorant(s). Theprecursor(s); cross-linker(s) and colorant(s) are as defined previously.Optionally the colorant is resin inactive.

The mixture of precursor(s); cross-linker(s) and colorant(s) used in thepresent process may further comprise one or more formulating agents, forexample one or more liquid(s), humectant(s) and/or surfactant(s) may beadded to the mixture to improve the solubility of colorant in theprecursor(s) and vice versa, and to improve the flow and handlingproperties of the mixture. The liquid(s) may be aqueous or organic (forexample as listed below).

Where a liquid(s) is added to the mixture the printed substrate may bedried by heating or by air drying at ambient temperature to evaporatethe liquid before the coating is cured or during curing.

The mixture of precursor(s); cross-linker(s) and colorant(s) maycomprise one or more pigments. Such pigments may be used in combinationwith dye(s) for shading purposes. Where the dye(s) is not significantlycoloured, i.e. it is an IR or UV absorber as described above, thepigment may be the sole colorant.

In the process of the present invention the printing process used isIJP. However may be that any printing process other than IJP could alsobe used in this process, such a flexographic, off-set lithographic,gravure, intaglio printing, ink-jet, dye diffusion thermal transfer andscreen printing processes. Preferably the printing process used isthermal IJP. It will be appreciated that although the precursors used inthe present invention are thermally ink-jettable, this does not precludetheir use in a non-thermal IJP process (such as piezo-electric IJP)where the printing conditions are less onerous on the precursor than inthermal ink-jet, or even in any suitable non-IJP printing process (suchas those listed above). The principles and procedures for ink jetprinting are described in the literature for example in High TechnologyApplications of Organic Colorants, P. Gregory, Chapter 9 ISBN0-306-43637-X.

A process for preparing an colour filter according to the presentinvention may comprise several steps.

The first step comprises making an ink containing one or morecross-linkable, thermally ink-jettable, water-dissipatable precursor(s)for cross-linked acrylic polymer(s), one or more cross-linker(s) capableof cross-linking the precursor(s); one or more colorant(s), one or moresolvents and optionally other formulating agents, by any method known inthe art.

The second step comprises adding to the resultant preparation (asappropriate for chemically or photochemically initiated systems) eithera radical source or a photopolymerisation initiator. An ink coloured inone of the desired colours can be produced, typically in the threeprimary additive colours of red, green and blue.

The third step comprises using the ink from step two to form a desiredpattern consisting of a multiplicity of discrete filter regions (pixels)on a transparent substrate via a single pass ink-jet printing process.Optionally, the transparent substrate has previously been subdividedinto discrete pixel regions by any method known in the art (for exampleformation of a black matrix by photolithography).

The fourth step comprises a curing step (for example heating,irradiating with UV radiation) on the patterned transparent substratecausing reaction of the precursor(s) and the cross-linker(s) containedin the pixels and thereby forming a continuous coloured film within eachpixel of the optical filter.

The fifth step consists of an optional baking step to remove anyresidual solvents and other volatile species from the films. Thisparticularly applies when the curing process in step four is other thanheating.

The steps described above may be followed for each of the desiredcolours to form a multi-colour optical filter structure so that thefilter structure finally comprises the transparent substrate and asingle layer of differently coloured pixels arranged in triads or in anydesired groups, each consisting of a predetermined number of differentlycoloured pixels.

However, it is preferable that the printing process employed achievesprinting of all three primary colours simultaneously. More preferably,an IJP process is used to form triads or any desired groupings of pixelsby using a printing head having appropriately designed outlets for thethree coloured precursor/colorant mixtures. The colours of thetrichromat can be additive (such as red green and blue [RGB]) orsubtractive (such as cyan, magenta and yellow [YMC]). Colour filters ofboth types are possible. Colour filters of the YMC type give brighterimages than RGB colour filters, but a poorer colour reproduction. Theyare useful in devices where maximum light utilisation is important, suchas reflective type liquid crystal displays.

In a further aspect of the present invention there is provided an inkwhich is effective for use in ink jet printing, the ink comprising afluid medium, one or more cross-linkable, water-dissipatable,precursor(s) for cross-linked acrylic polymer(s); one or morecross-linker(s) capable of cross-linking the precursor(s); andoptionally one or more colorant(s) or other active agent(s) (preferablya dye). The precursor(s); cross-linker(s) and colorant(s) are as definedpreviously.

Preferably the ink of the present invention comprises from about 40 toabout 99.6, preferably from about 70 to about 99.5, more preferably fromabout 75 to about 99, parts of the fluid medium; and from about 60 toabout 0.4 parts, preferably from about 30 to about 0.5, more preferablyfrom about 25 to about 1, parts of the precursor, cross-linker andcolorant; where all parts are by weight and the number of parts totals100.

Preferably the total concentration of solids in the mixture to beprinted [e.g. an ink comprising precursor(s), cross-linker(s),colorant(s) and/or formulating agent(s)] is from about 4% to about 50%,more preferably from about 8% to about 30%, most preferably from about10% to about 25% by total weight of the mixture, so the mixture isreadily printable using a thermal IJP head, whilst also being capable offorming the film coating in a single IJP pass. The solids content maycomprise either solely or mostly polymer(s) [e.g. those polymer(s) thatmay comprise the precursor(s)].

When the medium is a liquid, preferably the precursor, cross-linker andcolorant are completely dissolved, and more preferably they have asolubility in the liquid media at 20° C. of at least 10%. This allowsthe preparation of concentrates which may be used to prepare more diluteinks and reduces the change of the precursor, cross-linker and/orcolorant precipitating if evaporation of the liquid medium occurs duringstorage.

Preferred liquid media include water and a mixture of water and anorganic solvent. When the medium comprises a mixture of water and anorganic solvent, the weight ratio of water to organic solvent ispreferably from about 99:1 to about 1:99, more preferably from about99:1 to about 50:50 and especially from about 95:5 to about 80:20. Theorganic solvent is preferably water miscible.

When the liquid medium comprises water it may comprise one or more,preferably from 1 to 8, water miscible organic solvents.

Preferred water-miscible organic solvents may be selected from one ormore:

C₁₋₆alkanols (such as methanol, ethanol, n-propanol, iso-propanol,n-butanol, sec-butanol, tert-butanol, iso-butanol n-pentanol,cyclopentanol, cyclohexanol and/or tetrahydrofurfuryl alcohol);

amides, for example linear amides (such as dimethylformamide and/ordimethylacetamide) or cyclic amides (such as optionally substitutedpyrrolidones [e.g. 2-pyrrolidone, N-methyl-2-pyrrolidone,N-ethyl-2-pyrrolidone], caprolactam and/or 1,3-dimethylimidazolidone);

ketones and/or ketone alcohols (such as acetone, methyl ether ketone,cyclohexanone and/or diacetone alcohol);

water-miscible ethers, for example C₂₋₄ethers (such as tetrahydrofuranand/or dioxane);

alkylene glycols and/or thioglycols, for example those which comprise aC₂-C₆ alkylene group, [e.g. diols like C₂₋₁₂diols (such aspentane-1,5-diol, ethylene glycol, propylene glycol, butylene glycol,pentylene glycol, hexylene glycol and/or thiodiglycol)];

oligo- and/or poly-(alkyleneglycols and/or thioglycols), for examplediethylene glycol, thiodiglycol, triethylene glycol, polyethyleneglycol, polypropylene glycol and/or (polyols and triols) {such asglycerol and/or 1,2,6-hexanetriol}];

lower alkyl glycol and/or polyglycol ethers, for example C₁₋₄alkylethers of diols, e.g. monoC₁₋₄alkyl ethers of C₂₋₁₂diols: [such as2-methoxyethanol; 2-(2-methoxy ethoxy)ethanol;2-(2-ethoxyethoxy)-ethanol; 2-(2-butoxyethoxy)ethanol;3-butoxypropan-1-ol; 2-[2-(2-methoxyethoxy)ethoxy]ethanol;2-[2-(2-ethoxyethoxy)-ethoxy] ethanol and/or ethyleneglycol monoallylether];

cyclic esters (such as caprolactone); and

sulphoxides, (such as dimethyl sulphoxide and/or sulpholane).

More preferred water-soluble organic solvents are selected from: cyclicamides (e.g. 2-pyrrolidone, N-methyl-pyrrolidone andN-ethyl-pyrrolidone); diols, (e.g. 1,5-pentane diol, ethyleneglycol,thiodiglycol, diethyleneglycol and triethyleneglycol); C₁₋₆-alkyl monoethers of C₂₋₆-alkylene glycols; C₁₋₄-alkyl ethers of diols (e.g.2-methoxy-2-ethoxy-2-ethoxyethanol); C₁₋₆-alkyl mono ethers ofpoly(C₂₋₆-alkylene glycols); and mixtures thereof.

The inks according to a further aspect of the invention may be preparedby mixing the precursor, cross-linker, colorant, water andwater-miscible organic solvent in any order. Suitable mixing techniquesare well known in the art, for example agitation, ultrasonication orstirring of the components. The precursor may be present in the ink inany form suitable for IJP, for example the form of a dispersion,emulsification, suspension, solution or a combination thereof.Preferably the precursor is present as a solution.

The water-miscible solvent preferably has a solubility in water at 20°C. of more than 50 g/l.

Examples of further IJP-effective media for inks of the presentinvention comprising a mixture of water and one or more organic solventsare described in U.S. Pat. No. 4,963,189, U.S. Pat. No. 4,703,113, U.S.Pat. No. 4,626,284 and EP 0425150-A.

The amount of colorant, cross-linker and water-dissipatable precursorcontained in a liquid ink of the present invention will vary accordingto the depth of shade and properties required on the substrate.Typically, however, such an ink may comprise the following ingredients(where all amounts by part are the relative proportions of eachingredient by their weight):

(a) from about 0.2 to about 50 parts, more preferably from about 0.5 toabout 30 parts, most preferably from about 2 to about 25 parts,especially from about 5 to about 20 parts; e.g. from about 8 to about 15parts; of a water-dissipatable precursor which is polymeric (preferablyhaving a number average molecular weight less than about 20,000);

(b) from about 0.1 to about 30 parts, more preferably from about 0.5 toabout 25 parts, most preferably from about 0.5 to about 15 parts,especially from about 0.5 to about 10 parts; for example from about 2 toabout 8 parts; of colorant;

(c) from about 0.1 to about 30 parts, more preferably from about 0.5 toabout 15 parts of cross-linker;

(d) from about 40 to about 90 parts, more preferably from about 50 toabout 90 parts of water; and

(e) from about 0 to about 60 parts, more preferably about 0 to about 40parts, most preferably from about 0 to about 25 parts, especially fromabout 0 to about 20 parts of a water-miscible organic solvent;

The water-miscible organic solvent, mentioned in (e) above andoptionally present in these inks may each comprise a mixture of organicsolvents (such as one or more of those described previously).

Preferably the water miscible component “(e)” in the inks of the presentinvention may comprise from about 50% to about 100% (by weight) of awater-miscible solvent comprising:

(1) a cyclic ester and/or cyclic amide, more preferably an optionallysubstituted pyrrolidone, [such as, 2-pyrrolidone, dimethyl pyrrolidone,N-methyl-2-pyrrolidone,N-ethyl-2-pyrrolidone,N-(2-hydroxyethyl)-2-pyrrolidone and/or mixturesthereof];

(2) a water-miscible C₁₋₆-alkyl mono ether of a C₂₋₆-alkylene glycoland/or C₁₋₆-alkyl mono ether of poly(C₂₋₆-alkylene glycol); and/or

(3) any mixtures of (1) and (2).

The number of parts of the water-dissipatable precursor (e.g. an acrylicpolymer) is calculated on a 100% solids basis. For example 50 g of a 20%solids acrylic polymer is taken as 10 g of acrylic polymer.

The inks of the present invention may also contain additional componentsconventionally used in inks for IJP. Thus for example the ink maycomprise one or more: rheological agent(s) [such as viscositymodifier(s) and/or surface tension modifier(s), for example wax(es)(e.g. beeswax) and/or clay(s) (e.g. bentonite)]; corrosion inhibitor(s),biocides (such as those available commercially from Zeneca Limited underthe trade name Proxel GXL or from Rohm and Haas under the trade nameKathon); fungicide(s); kogation reducing additives; IR absorber(s) (suchas that available commercially from Zeneca Limited under the trade nameProjet 900NP); fluorescent brightener(s), (such as C.I. FluorescentBrightener 179); and surfactant(s) (which may be ionic or non-ionic andinclude surface active agent(s) wetting agent(s) and/or emulsifier(s)such as those described in McCutcheon's Emulsifiers and Detergents 1996International Edition or in Surfactants Europa 3^(rd) Edition 1996 eachof which is incorporated herein by reference).

The ink preferably has a pH from 3 to 12, more preferably from 4 to 11.The pH selected will depend to some extent on the desired cation for thecolorant and the materials used to construct the ink jet printer head.The desired pH may be obtained by the addition of a pH adjusting agentsuch as an acid, base or pH buffer. The amount of pH adjuster used willvary according to the desired pH of the ink, but typically a base may bepresent in an amount of up to 30%. Where a base is used this ispreferably the same base as was used to neutralise the anionicdispersing group during the preparation of the acrylic polymer.Preferred bases comprises 2-amino-2-methylpropan-1-ol and ammonia.

The ink may also comprise radical scavengers and/or UV absorbers to helpimprove light and heat fastness of the ink and resultant colour filter.Examples of such additives include:2-hydroxy-4-methoxy-5-sulfobenzophenone; hydroxy phenylbenzotriazole;4-hydroxy-TEMPO and transition metal complexes (such as nickel complexesof thiocarbamic acids). These additives are used typically in an amountfrom 30% to 60% by weight of the colorant, and are further described in“The Effect of Additives on the Photostability of Dyed Polymers”, Dyesand Pigments, 1997, 33(3), 173-196 and JP-A-04-240603 (Nippon Kayaku).

The viscosity of an ink of the present invention is preferably less than20 cp, more preferably less than 15 cp, especially less than 10 cp, at20° C.

The inks of the present invention have the advantage that they not onlyoffer improved operability in piezoelectric ink-jet printers, but arealso suitable for use in thermal ink jet printers as they have a lowtendency to block the nozzles of thermal ink jet printers. This isparticularly difficult to achieve for inks that contain polymers. Theprior art inks that contain water dispersible polymers work poorly oreven not at all in thermal ink-jet printers.

A further aspect of the invention provides a process for printing animage on a substrate comprising applying thereto an ink according to thefirst aspect of the present invention by means of an ink jet printer.

The ink jet printer preferably applies the ink to the substrate in theform of droplets which are ejected through a small nozzle onto thesubstrate. Preferred ink jet printers are piezoelectric ink jet printersand thermal ink jet printers. In thermal ink jet printers, programmedpulses of heat are applied to the ink in a reservoir (e.g. by means of aresistor adjacent to the nozzle) thereby causing the ink to be ejectedin the form of small droplets directed towards the substrate duringrelative movement between the substrate and the nozzle. In piezoelectricink jet printers the oscillation of a small crystal causes ejection ofthe ink from the nozzle. The term ink-jet printer denotes any devicewhich could use an IJP technique to produce an image.

A further aspect of the present invention provides a substrate which hasapplied thereon an ink of the present invention as defined herein and/orwhich has been prepared by the process of the present invention also asdefined herein.

The substrate, which is optionally transparent, preferably comprisesplastic or metal or glass, more preferably glass. Preferably the ink ofthe present invention has been applied to the substrate by a printingprocess, more preferably the process of the present invention as definedherein.

According to a further feature of this invention there is provided acolour filter comprising red, green and blue filter elements, or yellow,magenta and cyan filter elements, and comprising a coloured cross-linkedpolymeric coating on a transparent substrate prepared by the processdescribed in the present invention.

A further feature of the invention comprises a display containing acolour filter prepared according to the present invention.

A further feature of the present invention is a cartridge suitable foruse in an ink jet printer containing an ink according to the invention.Also there is provided an ink jet printer containing an ink according tothe invention.

The invention will now be described by example only. All parts andpercentages are by weight unless specified otherwise. In the examples(and previously), compounds referred to by reference to CI numbers arethe dyestuffs identified by these numbers in the Colour IndexInternational, 3^(rd) Edition, 3^(rd) Revision. In each of the followingExamples, the inks were tested and the results were set out in tables.

The result given in the second column headed ΔE_(ab) is a measure of thechange in L*.a*.b* co-ordinates (as measured with a Minolta CR-221chromameter) after the Example had been treated as described in thefirst column, where low figures indicate an Example with high fastness.

In the first column, the test denoted as “Xe light fastness” signifiesthat the ΔE_(ab) result was obtained after exposure of the Example to aXenon lamp over 100 hours in a Atlas Ci35A Weatherometer at thefollowing settings: lamp power 0.80 Wm⁻² at 420 nm, black panel 63° C.and wet bulb depression 16° C.

Each of the following Examples were tested for operability in a thermalink-jet head as follows. The ink was charged into a Canon BC-21e head,and 10 cm×2 cm blocks of solid colour were printed using a Canon BJC4300 printer. With each of the exemplified inks, 20 blocks could beprinted continuously without any deterioration in print quality.

EXAMPLE 1

An ink was made with the following formulation (all parts by weight):

Polymer A¹ 12.1 parts Primid XL552 (from EMS Chemie)²  4.0 parts Ammonia(0.88 specific gravity, S.G.) 12.1 parts Dye 1³  0.4 parts Dye 2⁴  2.8parts Ammonium dodecylbenzenesulphonate  0.4 parts Water 68.2 parts

Legend (Ex. 1)

1. Polymer A is a copolymer comprising 70 wt % methacrylic acid and 30wt % methyl methacrylate prepared by a catalytic chain transfer methodto give a polymer with M_(w)=1401 (M_(n)=588) as measured by GPC.

2. Primid XL 552 is a polyol cross-linking agent.

3. Dye 1 has the following structure:

 Dye 1 is synthesised in Example 3 of EP-A-0542420 (ICI/Zeneca).

4. Dye 2 has the following structure:

 Dye 2 was synthesised by condensing C.I. Reactive Blue 15 (availablecommercially from Aldrich Chemical Co.) with excess ammonia at 70° C. inan analogous manner to that described in JP-A-60-208365 (Nippon Kayaku).

For the purposes of testing the film fastness properties, the above inkwas coated on to microscope slides using a No.1 K-bar (RK Print-CoatInstruments Ltd.), and the slides cured at 200° C. for 15 minutes. Theresultant films had a thickness of approximately 1.5 μm.

The ink gave bright blue films with 77% transmission at 450 nm. Thefilms were subjected to the following fastness tests:

Test ΔE_(ab) 230° C. for 45 minutes 3.2 Dip in N-methyl pyrrolidone for5 minutes 2.5 Sonicate in water at 60° C. for 60 minutes; 700 W 0.4 Xelight fastness 2.0

EXAMPLE 2

An ink was made with the following formulation (all parts by weight):

Direct Yellow 86  2.8 parts Poly(acrylic acid) average M_(w) 2000 (fromAldrich Chem. Co.) 13.9 parts Primid XL552 (from EMS Chemie)  4.6 parts2-Amino-2-methyl-1-propanol  4.6 parts Ammonia (0.88 S.G.)  7.4 partsWater 66.7 parts

For the purposes of testing the film fastness properties, the ink wascoated on to microscope slides using a No.1 K-bar (RK Print-CoatInstruments Ltd.), and the slides cured at 200° C. for 15 minutes. Theresultant films had a thickness of approximately 1.5 μm.

The ink gave bright yellow films with 99% transmission at 600 nm and 0%transmission at 400 nm. The films were subjected to the following tests:

Test ΔE_(ab) 200° C. for 45 minutes 1.2 230° C. for 45 minutes 4.4 Dipin N-methyl pyrrolidone for 5 minutes, 3.2 then heat at 230° C. for 10minutes Sonicate in water at 60° C./700 W for 3 mins. 0.8 Xe lightfastness 13.4

EXAMPLE 3

An ink was made with the following formulation (all parts by weight):

Acid Red 52   2 parts Acid Yellow 23   3 parts Poly(acrylic acid)average M_(w) 2000 (from Aldrich Chem. Co.) 14.7 parts Primid XL552(from EMS Chemie)  4.9 parts 2-Amino-2-methyl-1-propanol  4.9 partsWater 70.5 parts

For the purposes of testing the film fastness properties, the ink wascoated on to microscope slides using a No.1 K-bar (RK Print-CoatInstruments Ltd.), and the slides cured at 200° C. for 15 minutes. Theresultant films had a thickness of approximately 1.5 μm.

The ink gave very bright red films with 98% transmission at 640 nm and0% transmission at 550 nm and 450 nm. The films were subjected to thefollowing fastness tests:

Test ΔE_(ab) 200° C. for 45 minutes 2.5 230° C. for 45 minutes 6.9 Dipin N-methyl pyrrolidone for 5 minutes, then 5.9 heat at 230° C. for 10minutes Dip in water at 30° C. for 5 minutes 0.3 Xe light fastness 5.1

Comparative Example A

An ink was made with following formulation in a similar method to thatdescribed in EP-A-0764290 (Zeneca), (all parts by weight):

Neocryl XK69/Cymel 327 stock polymer precursor⁵ 50 parts Ethylene glycol20 parts Distilled water 23 parts Ammonia solution (0.88 S.G.)  2 partsAcid Yellow 23  3 parts Acid Red 52  2 parts

Legend (Comp. Ex. A)

5. The stock polymer precursor was prepared as described in Example 3 ofEP-A-0764290, where Neocryl XK69 is a styryl-(meth)acrylate co-polymer;and Cymel 327 is a melamine-formaldehyde condensate included as across-linking agent.

When tested for operability in a thermal head as described previously,this ink (which comprises a total of about 5% by weight ofmelamine-formaldehyde resin) failed to print a single block of colour.

EXAMPLE 4

An ink was made with the following formulation (all parts by weight):

Polymer B⁶ 12.7 parts Primid XL552 (from EMS Chemie)  4.2 parts2-Amino-2-methyl-1-propanol 12.7 parts Acid Red 289  1.7 parts AcidYellow 23  3.4 parts 4-Hydroxy TEMPO  1.5 parts Ammoniumdodecylbenzenesulphonate  0.8 parts Water   63 parts

Legend (Ex. 4)

6. Polymer B is a copolymer comprising (by weight) 46.4% methacrylicacid and 53.6% methyl methacrylate prepared by a catalytic chaintransfer method to give a polymer with M_(w)=1607 (M_(n)=670) asmeasured by GPC.

For the purposes of testing the film fastness properties, the ink wascoated on to microscope slides using a No.1 K-bar (RK Print-CoatInstruments Ltd.), and the slides cured at 200° C. for 15 minutes. Theresultant films had a thickness of approximately 1.5 μm.

The ink gave very bright red films with 91% transmission at 620 nm and1% transmission at 550 nm and 450 nm. The films were subjected to thefollowing tests:

Test ΔE_(ab) 230° C. for 45 minutes 3.2 Dip in N-methyl pyrrolidone for5 minutes 1.7 Sonicate in water at 60° C. for 60 minutes; 700 W 3.2 Xelight fastness 4.2

Inks

Further inks which are suitable for making colour filters may beprepared having the formulations described in tables below where thenumbers denote parts by weight of each ingredient in the formulation.The dyes used may be in their free acid form and/or in the form of anyIJP-effective salt. The following abbreviations are also used in thetables:

DB199 = Direct Blue DB86 = Direct Blue DB87 = Direct Blue 199 86 87 AB9= Acid Blue 9 RB15 = Reactive Blue AR1 = Acid Red 1 15 AR52 = Acid Red52 AR289 = Acid Red RR4 = Reactive Red 4 289 AY23 = Acid Yellow 23 DY86= Direct Yellow Dye 1 = Dye 1 of 86 Ex. 1 A = Polymer A of Ex. 1 B =Polymer B of Ex. 4 PAA = Poly(acrylic acid) X = Primid XL552 of M_(w)2000 TEA = Triethanolamine TMP = Trimethylol- W = Water propane NMP =N-methyl-2- 2P = 2-pyrrolidone pyrrolidone BE = Butoxyethanol DEG =Diethylene GBL = γ- glycol butyrolactone. ADBS = Ammonium dodecylbenzenesulphonate SDBS = Sodium dodecylbenzene sulphonate SURF = Surfynol 465(Non-ionic surfactant available from Air Products) AMP = 2-Amino-2- AM =Ammonia methyl-1-propanol (0.88 S.G.) HT = 4-Hydroxy- TEMPO; and HMBS =2-Hydroxy-4- methoxy-5- sulfobenzophenone.

TABLE I DB199 DB56 AR52 AR289 A X W BE ADBS AMP AM 3 0.5 15 5.5 60 1 153 0.25 12 4 69.25 5 0.5  6 3 1 12 6 62 5 1 10 2 0.2 4 1 88.8 1 3 4 0.510 2 74.5 2  7 3.5 0.3 12.5 4 61.4 5 0.8 12.5 2.5 8 2 80.5 2 5 3 11.56.5 63 5 11 0.5 3 13.7 4.3 63.8 0.7 14 3 15 5 61 1 15

TABLE II DB199 AR289 A B PAA X TEA TMP W 2P ADBS AM 4 0.5 14 5 61.5 1 144 0.5 10.5 2.5 70 4 0.5  8 3.5 0.25  3 12 5 60.5 0.75 15 3 12 3 67 5 102.5 12 2 2 76 0.5  5 1  4 4 5 81 1  4 3 0.1 15 5 63 0.9 13

TABLE III DB199 AR289 B TMP W 2P DEG GBL SURF SDBS AMP 4 0.5 16 4 54.5 51 15 3 12 3 71.2 0.8 10 2 3 14 7 49 5 5 15 1 0.1  4 1 87.4 0.5 1.5 0.5 4 2  8 3 80.5 2 0.5  4

TABLE IV AR1 RR4 AY23 DY86 B X W DEG SURF AMP AM 2 3 10 5 69 1 10 1.5 314.5 5 62.5 3 0.5 10 5 18 7 50 5 15 1 1 3 12 4 64.5 2 0.5 12 2.5 2.5 157.5 56.5 1 15 3 10 5 74.2 0.8  7 4 10 3.5 67.5 5 10 4 1 1 15 5 63.3 0.710

TABLE V AB9 RB15 AY23 A PAA X W BE GBL SURF SDBS AM 2 5 13 4 55.2 5 0.815 2 3 15 5 59 5 1 10 3  8 4 74.5 2.5 2.5 0.5  5 2.5 10 3 69.5 4 0.5 0.510 2 2  5 10 7.5 52.5 1 20

TABLE VI DYE DB87 AR52 1 A X W HT HMSB ADBS AM 3.5 0.25 13.5 4 63.5 1.750.5 14 3 15 5 60 1 1 15 4 0.5 12 6 65.5 12 5 0.25 12 5 66.9 0.85 10 2.512.5 4 68 1 12 2.5 15 4.5 65.5 1 0.5 1 10 3 0.3 12 4 67.8 0.9 12

TABLE VII AR1 A B X TEA W HT HMSB NMP BE ADBS AM 4 15 5 53.5 2 5 0.5 155  6  6 5 64 1 1 2 10 5 12 2 2 64 2.5 2 2 0.5  8 2.5 13 4.5 63.5 1.5 114

What is claimed is:
 1. A process for preparing a patterned,cross-linked, acrylic-polymer, film coating on a substrate; the processcomprising: a) applying to the substrate by an ink-jet printing processa mixture comprising i) one or more cross-linkable, thermallyink-jettable, water-dissipatable, precursor(s) for one or morecross-linked, acrylic-polymer(s); ii) one or more cross-linker(s)capable of cross-linking the precursor(s) for the acrylic-polymer(s),where the cross-linker(s) is other than an epoxy resin and comprises oneor more; polyol(s) comprising three or more hydroxy groups;trimethylolpropane; and/or triethanolamine; and iii) one or more resininactive colorant(s); and b) thereafter curing the mixture in situ toform the patterned, cross-linked, acrylic-polymer, film coating on thesubstrate.
 2. An ink-jet printing process as claimed in claim 1, whichis a thermal ink-jet printing process.
 3. A printing process as claimedin claim 1 or claim 2, in which the mixture is applied by the printingprocess in a single pass.
 4. A process as claimed in claim 1 or 2, wherethe precursor(s) comprises one or more polymer(s) having a numberaverage molecular weight (M_(n)) of less than about 20,000.
 5. A processas claimed in claim 4, where M_(n) of the precursor(s) is from about 200to about 20,000.
 6. A process as claimed in claim 5, where M_(n) of theprecursor(s) is from about 200 to about 10,000.
 7. A process as claimedin claim 6, where M_(n) of the precursor(s) is from about 350 to about2,000.
 8. A process as claimed in claim 1 or 2, where the totalconcentration of solids in the mixture to be printed is from about 4% toabout 50% by weight.
 9. A process as claimed in claim 1 or 2, where theprecursor(s) for the acrylic-polymer(s) comprises one or morepolymer(s).
 10. A process as claimed in claim 1 or 2, where thethermally ink-jettable, precursor(s) comprises one or more olefinicallyunsaturated, water-dissipatable monomer(s) and/or one or more polymer(s)derivable from one or more olefinically unsaturated, water-dissipatablemonomer(s), the monomer(s) and/or polymer(s) optionally present inamount from about 20% to about 100% by weight of the precursor(s).
 11. Aprocess as claimed in claim 1 or 2, where the precursor(s) comprises oneor more: a) homopolymers and/or copolymers of: (meth)acrylic acid, vinylacetic acid, crotonic acid, itaconic acid, maleic acid, citraconic acid,fumaric acid and/or pentadienoic acid; b) co-polymers of the monomerslisted in (a) with other monomers, optionally selected from one or moreof alkyl(meth)acrylate, styrene and (meth)acrylamides; and/or c)monomeric poly carboxylic acids.
 12. A process as claimed in claim 11,where the monomeric poly carboxylic acids comprise at least butane1,2,3,4-tetracarboxylic acid.
 13. A process as claimed in claim 1 or 2,where the mixture of precursor(s) and cross-linker(s) is thermallycurable.
 14. A process as claimed in claim 1 or 2, where the colorant(s)are selected from the group consisting of: azos, anthraquinones,phthalocyanines, pyrrolines, thiophenedioxides, triphenodioxazines,methines, benzofuranones, benzodifuranones, coumarins, indoanilines,benzenoids, xanthenes, triphenylmethanes, nitros, nitrosonaphthols,phenazines, solvent soluble sulphur dyes, quinophthalones, pyridones,aminopyrazoles, pyrollidines, pyrroles, styrylics, maleimides,triphenazonaphthylamines, styryls, dithienes, azomethines, cyanines,pyrrolines and azoics.
 15. A substrate obtained by a process as claimedin claim
 1. 16. A substrate as claimed in claim 15, which comprises: acolour filter comprising a coloured, cross-linked, acrylic-polymercoating on a transparent substrate; and/or a transparent, coloured,cross-linked, acrylic-polymer coating on a substrate.
 17. A substrate asclaimed in claim 15, which has a utility as a component for a coloureddisplay.
 18. A substrate as claimed in claim 15, which comprises anarray of coloured trichromatic elements in which the trichromat isselected from the group consisting of: red, green and blue trichromat;and a cyan, magenta and yellow trichromat.
 19. A display which comprisesa substrate as claimed in claim
 15. 20. A display as claimed in claim19, which comprises a liquid crystal display.
 21. A process as claimedin claim 1, wherein the colorant comprises metallized azo.
 22. A processas claimed in claim 1, where the precursor(s) for the acrylic polymer(s)comprises one or more acrylic polymers.
 23. A process as claimed inclaim 1, wherein the one or more cross-linkers compriseN,N,N′,N′-tetrakis(2-hydroxyethyl)adipamide.
 24. A process as claimed inclaim 1, wherein the one or more cross-linkers comprisetrimethylolpropane, triethanolamine or a mixture thereof.
 25. A processas claimed in claim 1, wherein the one or more cross-linkers compriseN,N,N′,N′-tetrakis(2-hydroxyethyl) adipamide and one or both oftrimethylolpropane and triethanolamine.
 26. A composition capable ofbeing used in an ink jet printing process, the composition comprisingone or more cross-linkable, thermally ink-jettable water-dissipatableprecursor(s) for one or more cross-linked acrylic polymer(s); one ormore cross-linker(s) capable of cross-linking the precursor(s) where thecross-linker(s) is other than an epoxy resin and comprises one or more;polyol(s) comprising three or more hydroxy groups; trimethylolpropane;and/or triethanolamine; and one or more resin inactive colorant(s). 27.A composition as claimed in claim 26, wherein the one or morecross-linkers comprise N,N,N′,N′-tetrakis(2-hydroxyethyl) adipamide. 28.A composition as claimed in claim 26, wherein the one or morecross-linkers comprise trimethylolpropane, triethanolamine or a mixturethereof.
 29. A composition as claimed in claim 26, wherein the one ormore cross-linkers comprise N,N,N′,N′-tetrakis(2-hydroxyethyl) adipamideand one or both of trimethylolpropane and triethanolamine.
 30. An inkwhich is effective for use in an ink jet printing process, the inkcomprising a fluid medium and a composition comprising one or morecross-linkable, thermally ink-jettable water-dissipatable precursor(s)for one or more cross-linked acrylic polymer(s); one or morecross-linker(s) capable of cross-linking the precursor(s) where thecross-linker(s) is other than an epoxy resin and comprises one or more:polyol(s) comprising three or more hydroxy groups; trimethylolpropane;and/or triethanolamine; and one or more resin inactive colorant(s). 31.An ink as claimed in claim 30, which comprises: (a) from about 0.2 toabout 50 parts by weight of the thermally ink-jettable,water-dissipatable cross-linkable precursor(s) for the one or morecross-linked acrylic polymer(s); (b) from about 0.1 to about 30 parts byweight of the colorant(s); (c) from about 0.1 to about 30 parts byweight of the cross-linker(s) capable of cross-linking the precursor(s);(d) from about 40 to about 90 parts by weight of water; and (e) fromabout 0 to about 60 parts by weight of a water-miscible organic solvent.32. An ink as claimed in claim 31, which comprises: (a) from about 0.5to about 30 parts by weight of the precursor(s); (b) from about 0.5 toabout 25 parts by weight of the colorant(s); (c) from about 0.5 to about15 parts by weight of the cross-linker(s); (d) from about 50 to about 90parts by weight of water; and/or (e) from about 0 to about 40 parts byweight of the organic solvent.
 33. An ink as claimed in claim 30,wherein the one or more cross-linkers compriseN,N,N′,N′-tetrakis(2-hydroxyethyl) adipamide.
 34. An ink as claimed inclaim 30, wherein the one or more cross-linkers comprisetrimethylolpropane, triethanolamine or a mixture thereof.
 35. An ink asclaimed in claim 30, wherein the one or more cross-linkers compriseN,N,N′,N′-tetrakis(2-hydroxyethyl) adipamide and one or both oftrimethylolpropane and triethanolamine.
 36. An ink jet printer whichcomprises a composition comprising one or more cross-linkable, thermallyink-jettable water-dissipatable precursor(s) for one or morecross-linked acrylic polymer(s); one or more cross-linker(s) capable ofcross-linking the precursor(s) where the cross-linker(s) is other thanan epoxy resin and comprises one or more: polyol(s) comprising three ormore hydroxy groups; trimethylolpropane; and/or triethanolamine; and oneor more resin inactive colorant(s).
 37. An ink-jet printer consumablecomprising a composition comprising one or more cross-linkable,thermally ink-jettable water-dissipatable precursor(s) for one or morecross-linked acrylic polymer(s); one or more cross-linker(s) capable ofcross-linking the precursor(s) where the cross-linker(s) is other thanan epoxy resin and comprises one or more: polyol(s) comprising three ormore hydroxy groups; trimethylolpropane; and/or triethanolamine; and oneor more resin inactive colorant(s).